E. Rossoni and V. Blunda agree that the surname derives from a Germanic name composed of the elements ragin/ragan ("counsel," "divine counsel") and wald ("power, command, government").

Rossoni specifies that it derives from the medieval name of Frankish origin Rainoldus, documented in the Gesta Francorum. He adds that the line of the Rainoldi administered from the 17th century the fief of Caronno, in the Varese area.

Blunda, for the Sicilian variant, derives it from the Germanic compound Ragan Wald, with the meaning of "ruler of the divine counsel" or "lord of the counselling gods."

Blunda notes that this same combination gave the name Reinaldo (Reginald in English, Reinhold in German, Renaud in French), a central anthroponym of the medieval European epic cycles. Especially in the Carolingian cycle, Rinaldo of Montalban figures among the peers of Charlemagne as one of the most valiant knights, a source of inspiration for Boiardo and Ariosto in the Orlando Innamorato and the Orlando Furioso of the Italian Renaissance.